Real Estate and Lending Activities - Summary of Operations for Disposed Assets in 2018 (Parenthetical) (Detail) $ in Thousands			3 Months Ended	6 Months Ended	9 Months Ended
	Aug. 31, 2018 USD ($) Hospital	Mar. 31, 2017 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 Hospital	Sep. 30, 2018 USD ($)
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain on sale of real estate		$ 7,400
Germany [Member] | Acute Care Hospital [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Straight-line rent and other write-offs			$ 2,500		$ 7,600
Gain on sale of real estate			$ 695,200		$ 719,400
Germany [Member] | Acute Care Hospital [Member] | Primotop Holdings S.a.r.l. [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of properties sold | Hospital	71			71
Gain on sale of real estate	$ 500